Machine and process for making cfllulose



/ March 13, E CZAPEK MACHINE AND PROCESS FOR MAKING CFLIJULOSE FlL-MSAND THE IJ IKEI Filed Aug. 5, 1940 2 Sheets-Sheet 1 INVENTOR ATTORNEYMACHINE AND PROCESS FOR MAKING CELLULOSE FILMS AND THE LIKE Filed Aug.:5, 1940 2 Sheets-Sheet INVENTOR ATTORNEY Patented Mar. 13,1945 I mournsAND PROCESS FOR MAKING can LULOSE FILMS AND THE LIKE I Emu Czapek, NewYork, N. Y. Application August 3, 1940, Serial No. 350,291

In G

. 7 Claims. This invention relates to a process for, and to an apparatusfor carrying out the process of, the

manufacture of films, foils, membranes, bands, sheets and the like fromsolutions of cuprammonium cellulose. This application is a continuationin part of my co-pending application, Serial No. 116,290, filed December17, 1936.

ermany December 17,1935

On the other hand, this method of working has not been adopted for thewet process, according to which-a viscous cellulose solution is causedto precipitate byseveral wet agents such as water, saline solutions,acids and alkalies, for the purpose of forming a film. Since thecellulose solution must be brought into contact with This invention hasfor an object the manu facture of foils, films, pellicles and the likeby pouring a ouprammonium cellulose solution onto a movable support,especially onto a molding belt, and coagulating and solidifying thepoured solution, and thereafter continuing the further treatments,mainly the regeneration of the cellulose on said support withoutdetaching the result-'- ing film strip from the support until thechemical .conversion,purification and the like are comstructure wasdetached from the support as soon pleted, so that after the detachmentpractically only washing and drying of the filmare still necessary.

These and other features, .capabilitiesandadvantages of the inventionwill appear from the sub-joined detail descriptioigof specific embodi--ments illustrative of apparatus for carrying out the processesof theinvention illustrated in the accompanying drawings, in which 1 Figures 1to 6 inclusive illustrate diagrammatically and by wayof example variousembodiments of the apparatus in side elevation: and

Fig. 7 is a diagrammatic sketch iilustrative oi the progress of dryingof the cellulose pellicle's.

As aforesaid, the present invention has for an: object the manufactureof fella-films, pellicles and the like by the so-called ,wet" processwhile using a support for the treatments of the film strip as long aspossible.

In the so-called dry" process, the advantage of working on a movablesupport as long as possible, has been recognized for a long time. Insuch cases the working operation is invariably the same, that is, aviscous solution of a cellulose ester in organic volatile solvents ispoured onto the pouring belt and solidifies during the travel of. thebelt in its path of movement due to the gradual evaporation of thesolvents. 8 ortly before the belt returns to the pouring d ce, theapplied coating is dried. so that it ca be detached from the support inthe solid condition.

The "dry" casting process there requires only the application of heatand efiluent air for the removal of the solvent vapour, so that theutilisation of the support until the finished film is detached wouldappear to be more or less compulsory from the outset.

a liquid for the purpose of coagulation, and every further phase of thetreatment requires renewed contact of the coating with various otherliq-' 'uids,' the support in the wet process, if at all was used for thecoagulation only, and the film as formed.

The value of said support in the further stages of the process was imuslost, and the film formed had to be passed, freely suspended andsupported at a few points by rollers and feed cylinders, through a largenumber of treatment baths. In such a process the film is exposed to allmechanical influences which may give rise to breakage, folding up, andthe like. In addition the tension, caused bymotion of the machine, wouldeffect an elongation in the longitudinal direction,

whereby of course a shrinkage in the transverse direction necessarily:ollows. This shrinking in the transverse direction in turn would causethe original film to shrink to a greater extent in the transversedirection than in the longitudinal direction, and thus, despite thepouring out of very wide film layers and accordingly wide moldingdevices, the finished product would turn out in the end to be arelatively narrow film. v

The present invention also avoids all these,

drawbacks, attendant on the one hand on freely suspended lengths offilm, and on'the other hand on premature detachment of the stillunconsolidated film, by utilizing the pouring support until the 'filrnhas been passed through all the necessary chemical treatment phases.

In order more clearly to understand the invention, reference is made tothe accompanying drawings, which illustrate diagrammatically and by wayof example, in Flgs'l to 6, various em bodiments thereof.

In said drawings, the following are denoted: the pouring device i, thepouring belt 2,'the guide drums 3, 4, 5, 6 and 'i, the spraying devices8 and 9, the receptacles ill for coagulation liquid,

.a detaching or stripping roller ii, a transferring roller I! for thetreatment liquid, couch roller or rollers It for draining of thetreatment liquid, a transferring belt it, the detachment at it of thesolid film strip from the support, the

perizedandregenerated into cellulose hydrate. The regeneratioiii liquidmay be also brought into contact with-the film structure by means of aspraying device I, as shown in Fig. l', a spreading solid film leavesthe belt on the detaching out this last wet phase oi treatment on the 1pouring support also, and in passing the washed from saidsupportdlrectly to the drying apthe no"opportunity oi'evaporating arrowsi8 and II to indicate the direction of W movement of the pouring belt.

In the embodiment shown in Fig. 4, provision is made for enclosing thebath container and for exhausting and recovering the evolved vapours 5through pipe l8 and fan IS.

The invention will now be described with reference to the followingexample:

A solution of cuprammonium cellulose containing approximately seven percent of cellu- 10 lose and five percent oiamm'o'nia, isspreadfout' bymeans of a slot'feeder ijorother suitablespreading device, see Fig. 1 onan endless mold-. ing belt 2. The belt moves by rotation 01' the- Idrums 3, 4 and 5 inthe'direction oi'the arrows 16 i6 and I1. The spreadout cellulose solution, by

travelling with the moving belts, reaches the downwardly disposed partof the path or movement between the drums 3 and 4, where the cel lulosesolution is first wetted with a coagulation 20 liquid consisting of asix per cent aqueous caustic soda solution initially to coagulate thesolution, and subsequently wetted with water or with a similar alkalinesolution but preferably of a lower concentration efiectively to solidifythe solution. The wetting operation is effected in Fig. 1 by sprayingthe coagulation liquid onto the cellulose solution by means of aspraying device 8, although the application can also be eiiectedotherwise, for instance by means of ap- 80 plying rollers l2, asillustrated as an instance in Figs. 3 and 6, wetted'with the desiredliquid.

Excess of this liquid is received in the receptacle ill, see Fig. l, oris removed by means or couch rollers is, see Figs. 2 and 6. as

The direction of motion of the supporting belt changes at the drum 4,see Fig. 1. The cellulose solution is thus now coagulated on the belt.

Shortly afterwards, and during its passage through the zone between thedrums 4 and 5, the 1 film structure previously coagulated and therebytransformed into a film, is treated with a tour per cent aqueoussolution of sulphuric acid by mean'sof which saidfilm structure isdecopdevice,- s renting roller i2, as shown in Figs.

3 -and; -.a*iel tjbelt, H as shownin Figs. 2 andg5 r glily soakedmiththe regeneration ,liich, roller and belt press against turfejromtheoutside.

Thereupbn tha'regenerated and ,decopperized ing or stripping roller II,as shown in Figs. 1

" ted, to besubiected to'iurthe'r treatments, in-

cluding rinsing and-drying treatment.

'Aftercompletion oi the chemical treatment, the film consisting ofregenerated cellulose has already sufiicient strengthto preclude allfear or breakagelin the freely suspended portion'during. the, washingand drying treatment. Moreover, thereis no objection in princip'letovcarry- The improved drying. pr cess or the present invention proceedsfrom the iact that the cellu- 7 lose'film, since itis nota porousmaterial, be-

haves in a-manner iundainentally' diner-ent than that of paper or-textileiabric. during the mine process. '1'he"watet present in theinterior 01 through any pores or intention, but must esca e duringheating through thewhomogeneous surface of the film structure. 1

' It is known that with cellulose films the surface dries more quicklythan the inner layers.

Furthermore, the drier that the surface is, the

' greater is the resistance that it ofiers to the diffusion of the waterincluded in the interior.

The initial drying process accordingly counteracts the subsequentevaporation or the water present in the interior of the film, whichnaturally also retards the dryingprocess and also gives rise toundesirable difierences in tension between the surface and the innerlayers of the I film, the result being the known irregularities in Yshrinking, deformations, creases and'stresses'in the finished film.

It has now been ascertained in'accordance with the presentinvention'that the described dimculties can be avoided and the dryingeflected more rapidly and economically by conducting the dry- .ingprocess in such a manner as to avoid hardening or the-surface by saiddrying. The present invention achieves this by commencing the dryingin amoist atmosphere saturated with water vapour and only reducing thevapour content of this atmosphere as the drying progresses. The warmingor the film structure and the moisture contained therein to thenecessary evaporating temperature is efiected according to the presentand the temperature or the vapour atmosphere on the other hand, shouldbe adjusted in relation to each other and both should be adjustedrelatively to the vapour content of theheating atmosphere in such amanner that the foregoing favorable difiusion process may take place.

The present invention therefore provides a process for drying cellulosepellicles and the like, in which the drying process, is commenced byheating the wet cellulose structure by means of a heated vapour orheated atmosphere and for a heated drying support for the cellulosestructore. up to the particular temperature oi drying desired, whichvapour atmosphere in relation to the filmtemperature at the time is atleast saturated with vapour, and than continuing the drying process, ifthe film structure is heated to thepredetermined drying temperature bygraduv ally allowingthe vapour content to fall in accordance with'theprogress of the drying oi the film structure, that is in accordance withthe progress of the. diffusion or the water vapour from the interior tothe surface of the film structure. The

drying temperature will during this time remain practically constant.

The surprising result'ot this process is shown in the diagrammaticsketch, Fig. 'I, attached hereto, in which diagram the drying time andthe degree oi drying out at any time are plotted as '"'o'rdiiia'te'andabscissa respectively. The two curves show the progress oi'the drying inaccordance with the former principle (a) and the prin; ci'pleunderlyingthe-inv'ention- (b) Whereas" in the case of theiormer dryingprinciple the 'amountof water evaporated is initially many times largerthan that in accordance with the ini vention, nevertheless in'the newmethod 0! workas'rniss in: as the curve shows. the drying process iscompleted considerably earlier than hitherto. The progress of the curve(in, which is almost a straight-line, shows how uniform is the drying.and investigation of the thus dried product confirms that it is alsofree from tension, it does not split when out, and is-more resistant totearing than the hitherto known products.

The present invention, owing to the resultant economy in heat andshortening of the drying time. unites the advantage ofan economicalworking withgthatpi products'ioi improved quality. Thepresentprocess canin general be car-' ried out on anymachine or apparatus, which enablesthe pouring supportto be passed through clined direction for the firstportion at least and for themaior portion of its travel through theprecipitatingbaths. v

This arrangement also affords the advantage that the film precipitatedon the surface of the belt does not sag downwards in along horizontal 1stretch, but receives better support on the drums. It therefore does notpossess any tendency to detachitself from the support orto tear owingto' its dead-weight, but lies against the belt. Moreover thisarrangement permits a compact and comp'endious construction particularlyin belts of the various -treatment liquids necessary for the formationof the film, or to allow said liquids to act ina suitable manner on. thefilm engaging, and 'formingon, said support for example by g. Theordinarily used type of belt pouring machine, such' as is used for themanufacture of acetate foils and photographic films by the dry" method,cannot be used for the "wet process of the present invention owing to.the necessity for treating the film with several wet reagents, asmentioned-above. These belt pouring machines p with two guiding drumsfor the pouring belt have not'hitherto been used in practice for the wetprocess,- because it is not easy to solve the problem of installing, thedrums and the lower half of the pouring belt with respect to the usualconstruction of the apparatus. More- 50 and 100 yards in length. Finallyit is possible with this-arrangement to enclose the liquid container ina simple and ingenious manner so that y it is possible to exhaust andrecover the vapours.

The pouring belt and/or the drums may be heated or cooled in a mannerknown per so. For

the supporting belt and the drums also nonover, the fiat elongated shapeof the aforesaid apparatus is not favourable for running a belt with afilm coating thereon through a precipitating bath'because the him has atthe underside and can therefore readily peel'ofl or fall of! from thesupport oi its ownaccord. A film coating so loosened or peeled offfromthe support gives difficult to avoid on account of the principle ofthe aforesaid pouring machine type.

A belt pouring machine, however, can therefore be used for this process,according to the present invention. Such machine fulfills therequirements. to-wit; that the poured cellulose solution coming intocontact with the treating liquids must not run oi! the belt and, when itsubsequently solidifies, that the resulting film structure should notbecome detached from the belt prematurely. To this end and in accordancewith said requirements, the apparatus of the present invention comprisesnot two guide drums for the belt as hitherto customary, but three ormore guide drums some of which, generally two, are mountedoutside of theliquid, while the others are accommodated completely or partially withincorrosive kinds of steel are preferably employed, or the'supporting beltand the drums are protected from the varying actions of the treatmentbaths .bymeans of non-corrosive coatings. I

In accordance with this invention, the drying may be carried out in"practice with any drying machine suitable for drying this product, hn-

proved by modifications of individual parts and by supplementary.mechanical devices. ample, a" cylinder drying machine heated with steam,hot water, oil, and the like, is supplemented by a system of pipesthrough which there is blown onto or between each pair of the severalcylinders, air at the appropriate temperature, and of the requisitewater vapour content or else the drying machine is enclosed insurrounding walls in the manner customary in these drying machines.Partition walls 'are disposed at suitable places inside the surroundingwalls I which enable different vapour contents of the :4 rise toproducing the 'sametroubles asaceompany an unsupported film, and'whichalso are j surrounding atmosphere to be maintained. The necessaryadjustment, regulation and maintenance of this vapour atmosphere iseffected onv the one hand, by supplying varying quantities of dry air tothe separate'chambers, and on the other hand, by conducting away varyingquanti ties of the vapours evolved during drying.

It isobvious that various changes and modifications may be made to thedetails of construction without departing from the general spirit of theinvention as set forth in the appended r m1 s 7 FY a p i V l .i. Theprocess of'manuf mr NH ions. membranes, hands and the like, from cfmonium cellulose solution while continuously v supported duringcoagulation and regeneration, which comprises pouring the cellulosesolution onthe outer face of an endless. movable support to form alayer, coagulatingthe layer by a coagulating liquid while still on theouter face of the support, thereupon regenerating the layer socoagulated by a regeneratingliquid while still for the chemical processby the suitable location of the third or also of a fourth or fifth drum.

In accordance therewith, the pouring slit is located over the upper ordry" run of the pourin; belt, while the belt itself is guided in an inon the outer face or the support, and only then removing the layer soregenerated from-the initial support to prevent any interruption in supporting the layer before being finally removed.

2. The process of manufacturing foils, membranes, bends and the like,from a cuprainmonlum cellulose solution while continuously supportedduring coagulation and regeneration, which comprises pouringthe/cellulose solution on the outer face of an endless movable sup portto term layer, coagulating the layer by a coagulating liquid whilestlllon the outer of the support, thereupon regenerating the layer on theouter face of the support, thereupon washing the layer while still onthe outer face or the r awai s so coagulst'ed by a regenerating liquidwhile still on the outer face of an endless movable support toform-alayer. coagulating the layer by a cosupport, and only'then removing thelayer from for a drying on theouter face of an endless movable supportto form a layer, coagulating the layer by a coagulating liquid whilestill on the outer face of the support, thereupon regenerating the layerso coagulated by a regenerating liquid while still on the outer face ofthe support and the'ntrans ferring the layer so regenerated from theinitial support, the coagulating and regenerating liquids being appliedby spraying or the like. v

4. The process of'manufacturing films, foils, membranes, bands and thelike, from a cuprammonium cellulose solution while I continuouslysupported during coagulation and regeneration,

which comprisesipouring the cellulose solution on the outer face of anendless movable support to form a layer, coagulating the layer by acoagulating liquid while still on the outer face of the support,thereupon regenerating the layer so coagulated by a regenerating liquidwhile stillon the outer face of the support and then transferring thelayer so regenerated from the initial support, the coagulating andregenerating liq uids being applied by transferring the same onto thelayer from wetted transfer rollers or the like. 5. The process ofmanufacturing films, foils,

agulstingliquid while still on the outer face of the support, thereuponregenerating the layer" so coagulated by a regenerating liquid whilestill on the outer face of the support and then transierring the layerso regenerated from the initial support, the coagulating andregenerating liquids .being applied to the layer by transferring thesame from a wetted transfer belt or the like.

6. In an apparatus for the manufacture of extensive lengths of sheets,films and the like, the

combination of an endless supporting belt, guiding drums solely on theinside-of said endless belt for'movably supporting said belt, a pouringdevice for pouring a cellulose solution on the belt to form a supportedlayer, means for successively applying treatment liquids includingcoagulating and regenerating liquids to the supported layer without inany way interrupting its support on said single supporting belt, andmeans for finally removing the layer so treated.

'1'. In an apparatus for the manufacture of ex- 'tensive lengths ofsheets, films and the like, the

combination of anendless supporting belt and a drying apparatus, guidingdrums solely on the inside of said endless belt for movably supportin:said belt, a-pouring device tor'pouring a celmembranes, bands and thelike, from a cuprammonium cellulose solution while continuouslysupported during coagulation and regeneration,

1 which comprises pouring the cellulose solution lulose solution ontothe belt to form a supported layer, means for successively applyingtreatment liquids including coagulating and regenerating liquids to thesupported layer without in any way interrupting its support on saidsingle supporting belt, means for washing thelayer while stillsupported, on said belt, and means for finally removing the layer fromsaid belt and transferring it to the drying apparatus.

EMIL CZAPEK.

